


The meaning of destiny

by Animillion



Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Angst, Angst to come, Cute, Discord: The Kingdom of Shipping (Dr. STONE), Highschool AU, Jogging, M/M, Modern AU, Non explicit mma fight, Rating subject to change, Soulmark AU, Soulmate Theory, Soulmates, TKS, TheKingdomofShipping, happy feelings, slow burn?
Language: English
Status: In-Progress
Published: 2020-09-28
Updated: 2021-01-10
Packaged: 2021-03-07 17:33:39
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 7,956
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26691481
Author URL: https://archiveofourown.org/users/Animillion/pseuds/Animillion
Summary: Tsukasa and Senku never thought they would actually meet their soulmate. What does destiny and fate mean anyways? Sure they’re connected, but that doesn’t mean they’ll love each other right? Surely not.
Relationships: Ishigami Senkuu/Shishiou Tsukasa
Comments: 14
Kudos: 70





	1. Chance meeting

“E=MC^2” Tsukasa remembers the first mark he had ever gotten from his soulmate. It had been on a wet rainy day when his sister had just gotten diagnosed with her illness. 

“Oh! So she was cheating on a test?” A girl in the class poses with a snicker. It’s free period and they’re talking about soulmates and the first thing they ever got written onto them by their soulmate. Tsukasa was new. He had just transferred here because of the convenience of where his sister had been moved. 

He smiles politely to her, not really minding the nosiness, “no, I don’t think so, more like writing it down because they didn’t have paper.” A self note that had accidentally come through. That was how it had felt.

“Ah yeah hand notes do come through too huh.” One of the guys says, looking at his palm and then the back of his hand. 

Tsukasa looks down at his broad palm. There hadn’t been many notes recently. Not even doodles of rocket ships and lab experiments to cross his forearm. He knew his soul mate was probably busy, but he can’t help but wonder with what. 

“Senku! Hey!” A loud boy with glasses shouts out the door as he watches someone go by. It looks like an underclassman. 

The boy pulls him into the room without warning and this Senku looks pretty annoyed with the endeavor brought on him. “I’m kind of busy right now-“

“Cmon just a second of your time president?” Senku looks at him and sighs. “Great! You’re better at explaining the whole soulmate thing better than I am.” 

“Did you mean the electromagentic brain wave phenomenon theory?” It was such a long name. “It’s a bit much to call them soul mates, but whoever your brain is tuned into does have a striking similarity with you.” 

The upperclassmen seemed intrigued enough at his words. Tsukasa relaxes and turns to listen in as well. He’d heard the theory before, but didn’t quiet understand it himself. 

Senku shrugs off his lab coat. He puts it aside and rolls up his sleeve. “The first recording of the phenomenon started around 300 years ago in a small town in what is now Quebec, Canada, a little girl was drawing on her arm beside a friend one day and suddenly it appeared on him as she drew.” 

“The mother of soulmates.” Tsukasa says. 

“That’s what you could call it,” he nods, “the theory is that once you reach a certain age there’s a component in your brain that sort of... activates- scientists believe its puberty that kick starts a reaction for ones brain to send out electromagnetic waves.” Senku pulls a black marker from his pocket, opening it. “So the nerve endings on your skin is the first signal it sends to your brain, that then sends out in brain waves to someone who has the same fine tuned waves as your own- this is what we refer to as a soulmate.” He presses the marker to his forearm before dragging it up and along in demonstration. As if the crowd of upperclassmen haven’t seen it in action before. 

Tsukasa is intrigued with the explanation but then his intrigued turns into anxiety. He feels something creeping along his forearm as he watches the under class-man draw a long doodle across his skin. It has to be a coincidence. But he looks at what’s showing from his wrist and there is no mistake. 

The group watches his arm a minute. Senku hums, a bit upset there is no immediate response. “Ah, looks like they’re busy, I’ll just go ahead and explain the rest anyways- so the signal marks your soul mate with the same thing you’ve pressed into your skin- remember it’s not just ink that comes through, anything that stains the skin will do- and on the receiving in they cannot wash it off until the original mark is gone.”

“So your brain just stains someone else’s skin too?” One of the girls clicks her tongue, “interesting theory.”

“It’s only in the works,” he assures her, “they haven’t made anything that can actually identify these brain waves as of yet.” Who knew what power someone with that knowledge could hold. “If that’s all then I’ll be going, see you in science club Ken- you guys should consider joining.” He was in a hurry to leave. 

“That president of yours is really brainy.”

“Ah, he explained it super simple, guess he wanted to leave soon.” The glasses boy who had originally brought that guy in here sighs in defeat. 

Tsukasa is watching the door in awe. His soul mate. That was... his soul mate. 

His eyes glance down at the chair in front of him. The white lab coat is sat wrinkling away in it. While the others aren’t looking, he tucks it away in his desk. He needs a reason to approach Senku.

\- - -

The halls were quiet, but Tsukasa knew Senku was here. He looks at the red pen on the back of his hand. 

_You there?_ It asks. 

He received it only moments ago. Usually he would have responded back to Senku by now. Senku. He had a name for him. 

He holds his lab coat close to him. It smells like linen and chemicals. He has a smell for him. 

Science room A. He looks up at it and takes a deep breath before knocking. 

“Come in?” Of course he’d be confused as to why he’d knock on a door if the room was for all student use. 

Slowly he opens the door and as he had guessed it, Senku was there despite it being past club hours. He’s tinkering on some sort of machine. Tsukasa doesn’t know what to make of it at all- it looks like something out of a sci-fi movie. He closes the door quietly just standing there until Senku bothered to look at him. 

“Oh, it’s you,” he blinks and realizes he had never even gotten his name, “Ken’s friend right?”

Tsukasa feels his tongue dry. Regardless he lets out a sigh and shrugs, “I don’t know if I’d call him a friend, I just transferred here.” 

“Okay, then you are...”

“Shishiou Tsukasa- but... you can just call me Tsukasa.” 

“So familiar even though we’ve just met?” He smirks and laughs, “I’m Senku.” 

“I know.” The name had been playing in his mind all day. Senku. Senku. Senku. That was his soul mates name. He smiles soft at the thought. But he knew he was coming off as a bit weird to the other. He could see it in the way he leans away from him. “I, uh, was coming by to drop this off.” He holds up the lab coat. Senku was already wearing one, but it was probably a spare from the lab. 

“Oh, hey thanks I was wondering what I did with this thing.” Senku comes closer and takes it from his hand. “Thanks Tsukasa,” he pauses, “So are you thinking about joining the science club?” 

Tsukasa doesn’t have the time for clubs. Not between his real training and hospital visits. But he still found the time to come here today. He had to come, there was no other time to. 

“I, no, but I did want to speak with you about earlier- about soul mates... in your professional opinion, do you think they’re real?”

Senku laughs and holds up his hands, “woah hold on there I’m not a professional by any means.” He shakes his head but thinks a minute. “Based on recorded evidence, yes, I would say the person you are linked to could be considered your soulmate- the mother of soulmates grew to love and cherish the boy who was next to her that day after all- they got married, had kids, and hid it all in order not to be hunted for witch craft.” 

“There’s something I want to show you.” Tsukasa begins to undo his jacket. Senku makes a choking noise. He knew what this looked like after having said those words specifically, but he needs him to see it all. Once his jacket is slid into his arm he starts to unroll his sleeve. 

“What are you..” those ruby orbs go wide when Tsukasa turns his muscled arm to reveal the black doodle going down his forearm. 

“This is the mark you made earlier, right in front of me.” He smiled. 

“Right in front of you...” Senku rolls up his sleeve to look at the same mark. He swallows thick and grins. “Now this is the type of thing that gets me excited Tsukasa.”


	2. Sisters and soul mates

_Meet me in the school lab after 7?_

Tsuaksa looks down at his sweaty forearm. Blue ball point pen this time huh? Ever since he and Senku had met, he didn’t know what to think. Senku was an eccentric, stubborn scientist. Tsukasa had to wonder why the hell he was in _high school_ and not some amazing university program. But they had only just met. 

He laughs at the time given. 7pm? Wouldn’t the school be closed up? 

Senku had his number, but Tsukasa knew the other valued efficiency. Tsukasa only nods to his arm. He’s been thinking about Senku’s words. How one could call this phenomenon _soulmates_. Was Senku really his soulmate? Did he want to be? Well, for now he believes he does. Senku had been non stop that day in the lab. 

Marking up and down both of their arms to test things out on him. Seeing if writing on Tsukasa himself worked (it hadn’t). Going on about how they needed to get their hands on brain wave indicating technology. 

It wasn’t like how Tsukasa thought it would be at all. The teen knew his soulmate was smart. Years of skin marked notes, light chatter, rocket ship doodles. But he had never thought their relationship would immediately be so superficial. 

He sighs low to himself. Perhaps it was him who was the problem? Just going along with what Senku wanted? 

He shakes off his thoughts. Even if the scientist wanted so much studying through him, he didn’t have time for that today. He sets a weight against the floor. 

Sweat drips down his face. Slow breaths coming from him. The apartment is quiet tonight. As it always was. Now having legal custody of his sister and moving out of the house, living alone was very quiet. It reminds him too much of the times just after his sister was hospitalized. When he had returned home, nothing was the same. 

Tsukasa wipes the sweat from his brow. He picks up his phone and it’s not hard to find Senku’s number, he had been texting him all week now. 

_”Hey, Tsukasa, did you get my message?”_

He always sounds tired. If he sat down and took a breath for two seconds, Tsukasa thinks he might explode.

“I did, but I’ll have to decline, I have some important business I have to attend to.”

There’s an annoyed groan on the other end. Tsukasa frowns. Was he about the be told to cancel? Like those have done in the past?

_”Cancelling my date plans?”_ The groan had turned into a snicker. Tsukasa’s face heats. He had been saying stuff like that so lightly. _”Fine fine, I get it you have your own life... so when will you be free?”_

He sighs in relief. 

“I won’t be busy all evening, I’ll be finished by nine.”

_”Great! Wanna come over? There’s no way we’re getting into the school by then but I can make do at home anyways.”_

Tsukasa chuckles at this as he makes his way into the kitchen. He cracks open an orange juice and sips at it. 

“Trying to get me in your bed so soon?” He hears Senku choke on the other end. Well, Tsukasa didn’t think there was any harm in just coming over. Although he thought mentioning the time would make Senku drop it and ask on a different day. “Sure Senku, I’ll come over.”

_”That first comment better have ten billion percent been a joke- I’ll text you my address.”_

“I’ll see you,” Senku says his goodbye and moments later Tsukasa has his address in a text. 

He laughs under his breath. What would Senku’s parents think having of his soulmate over so late? If he didn’t go, he’s sure Senku would let him have it. Tsukasa can’t believe he agreed to it. But he couldn’t say he wasn’t looking forward to spending some time with another person. 

• • •

Of course, after visiting the hospital he would feel so depressed. It was routine after all. Go to the hospital, greet the familiar nurses and doctors. Sit by his sisters bedside and simply... talk. Maybe it wasn’t healthy. But it was cathartic at the least. 

Seeing her lay so peacefully. Her heart is beating. And there’s minimal brain activity. But it’s still brain activity right? Scientific advancement seemed to surround his life. And now as he makes his way towards his soulmates home, he supposed that was his fate. There’s a twine of hope that maybe, just maybe, Senku would one day be able to achieve the impossible. But he lets his hope die as quick as it comes. Like he always does. 

As he sees the other come into view from the entrance of the apartment complex he takes a breath. This was better than going home to an empty house at least. Someone with cognitive thought needed him. 

Senku yawns as he waves a greeting. 

“It’s late for meeting up don’t you think?” Tsukasa asks, “how did you even plan to get into the school at 7 in the evening?”

“If you’ve done it once you’ve done it a million times Tsuaksa.” The scientist reassured him. He nods his head in the direction to follow. 

The complex is quiet, save for some televisions that have their volumes up way too high. When he’s inside he takes off his shoes, excusing himself for the intrusion.

But this home too, is short of any noise or life. It’s only them. Tsukasa takes a glance around. The portraits against the wall are perfectly dusted off. The walls and floors are spick and span. There’s two pairs of shoes at the door. His and Senku’s. 

“Your parents aren’t home?”

He asks as they pass the living room. There’s papers scattered on the coffee table. They don’t look significant. The television looks like it was recently used- a game cube sat in front of it with two stray controllers with no owners to hold. 

“Ah, it’s just me and my old man, but he’s in Russia doing his final steps to go to space.”

Tsuaksa blinks. “Space? So he’s an astronaut? So brains runs in the family?”

Senku laughs as he grabs the door knob to one of the rooms. He turns his head to Tsukasa and raises a brow. 

“Oh that guy totally only got in by luck,” he turns the knob and opens the door, “besides even if he were some genius scientist it must’ve been passed down by a miracle.” Tsukasa isn’t sure what he means by that but doesn’t get an answer. 

The room is full of science projects. Algorithms written across white boards. There’s a desk and a computer set up, but surrounding it is a chaotically organized mix of circuit boards, tools, and pens with chewed tips.   
The floor is at least clear, aside from things that sit against the wall. He marvels at it all. Even the built rockets that look charred from failed take off amaze him. 

“You gonna take a picture or somethin?”

Tsukasa swallows and shakes his head. 

“I should’ve expected you had quite a show room.”

“Show room?” He clicks his tongue, “you expecting a lap dance Tsukasa? Come on keep your head in the game.”

Ah, Senku was all about teasing wasn’t he? 

“And that game would be...?” 

Senku smirks like the devil. Tsukasa wonders if he should’ve even asked. The scientist grabs a helmet device from his desk and holds it up to Tsuaksa. It looks kind of funny. Like something you see in a sci-fi movie but a little less cliche. 

“Modern brain wave sensors are typically designed to find abnormalities in the brain to help find the cause and duration of certain symptoms in ill patients, it’s kind of hard to predict where the waves are coming from with just the normal ones- this design is supposed to get a full 360 degree of you noggin Tsukasa.” 

Oh, right, _this_ game. Tsukasa is handed the helmet. He doesn’t quite get it. Why Senku was so hellbent on finding the cause for soulmates. Maybe it really was just that? Spirituality of two close souls bonded together for eternity? 

He quickly deduced Senku wouldn’t accept that as an answer. If he did find out the cause of soul mates... then what? Would he try and free humanity of them? Tsukasa knee plenty of people that saw soulmates as illness. Typically older people who didn’t have soulmates. Or had soulmates who they fell out with in horrible ways. Was this what Senku’s goal was?

“Don’t worry Tsukasa, I don’t think soul mates are illnesses.” 

Tsukasa covers his mouth. Had he said that aloud? Senku grins at him as he hooks the helmets wires to his laptop. 

Senku takes out a black pen. Not any one though. One Tsukasa remembers quite fondly. Because it has sparkles on the top that appeared on his own skin. 

“You used that the day you told me you wanted to go to space right?”

Senku laughs, “well, the old one ran straight out of ink, but I guess you could say it’s like the same one, you remember it?”

“Yes,” he replies, “I thought about how my sister might like the way it glitters.” And when she wakes again, he’ll give her a thousand markers like that. 

“Sister?” Senku tilts his head. Of course, Tsukasa never told him. He never tells anyone. 

“Yeah, she’s ten and loves pretty things.” Like seashells glistening at dusk and mermaids that enchant her sleeping dreams. 

Surprisingly Senku doesn’t pry. Just boots up the program. And as it begins to work, Tsuaksa dons the helmet piece like nothing ever happened. Like nothing of soul mates and sisters was ever said. He sighs. It’s better that way anyways.


	3. Sensor

Tsukasa looks at his soulmate with pity. As the clock strikes midnight it seems that the research has come up empty handed. Marks and doodles and frustration now harbor themselves on their skin. Nowhere visible when clothed of course.

Just along the legs and forearms. Senku had even taken his shirt off to continue his research. Seeing if different areas of the body caused any change. The only real change happened when he had suddenly unbuttoned his shirt in front of him. But of course, it was only Tsukasa becoming a bit flustered. 

Senku’s body was nothing short of well... what Tsukasa expected. He’s pale, white, hardly a sight of muscle on him. His hip and collar bones stick out like a sore thumb and he’s sure if Senku worked on it his abs would be pretty visible too. 

Tsukasa doesn’t have much body fat himself. So he only knew this from experience. 

Senku relaxes back in his desk chair. A frustrated sigh leaves him. 

“Well, it’s midnight, guess we can stop here.” 

It’s a relief to take the helmet off. It was annoying and cut off his corner view and made his forehead itch with sweat. Tsukasa lays it on the desk and pats the scientists shoulder. 

“Maybe next time.”

The promise of a next time seemed to get him in a better attitude at least. And just as he opens his mouth to make a quip, Senku’s stomach lets itself be known. 

He holds it and his brows knit together. 

“Ah, I forgot my dinner.”

Tsuaksa blinks. This well put together, always do things when necessary guy had forgotten his own dinner? Tsukasa had eaten light. Which he really shouldn’t have. He needs protein and energy foods to help his body shape his fighting form. Not a salad with vinaigrette dressing. 

And so like an infectious yawn, his stomach also growls like a hungry wolf at witching hour. 

“Guess we’re eating a late dinner then.”

Senku stands, stretched, and puts his shirt back on. Tsukasa follows suit. 

In the kitchen Senku puts on a pot of boiling water and pulls out two packs of instant ramen. Something Tsukasa hadn’t even eaten in years. 

“For a scientist you sure eat healthy.” Tsukasa’s sarcasm isn’t met with a kind expression. Perhaps he should be nicer, after all, Senku doesn’t have to feed him.

“I’m a scientist, not a dietitian.” 

Tsukasa finds his mind wandering off in the in between as it always does. Eyes gazing around the kitchen. The old burner licking away at the bottom of the pot. The chipped paint in the cupboard door. The small dent in the fridge. The magnetic letters spelling out equations and dusted over like they’d been forgotten there some time ago. 

And without Senku’s chatter, the apartment is quite silent. 

There’s a tickle running up the side of his arm and he moves on instinct to squash a bug. Instead he’s met with writing. 

_Earth to Tsukasa._

Amber eyes trail to meet mischievous crimson ones. While mischievous as they were, the darkness under them seems to grow. Senku is tired. He’s a man of efficiency, but Tsukasa has seen him drink his fair share of energy drinks in the short time he knew him. 

“You know, if you keep only communicating with me by skin we’re both going to end up covered head to toe.” 

Senku shrugs, “eh, It’ll wash off, besides it got your attention didn’t it? Where were you?”

Tsukasa looks around the place and slowly raises his shoulders into a shrug. 

“It’s quiet is all.”

“It’s midnight in an apartment complex filled with mostly senior citizens,” Senku chuckles, “of course it’s quiet.”

Tsukasa looks at him a moment before nodding. Yeah. Yeah that makes sense. But he’s not fond of the quiet all too much. 

“Well, it’s not usually this quiet actually, Taiju is over here almost constantly so we have someone who can satiate your boredom if that’s a problem.”

Tsukasa new Taiju from the afternoons he visited the lab. Tsuaksa had put away some training time to help Senku out with his research. Taiju was an easy sort to get along with. Honestly he could do most of the talking if you let him. Which was fine by Tsukasa. 

He’s unsurprised of this news. Taiju and Senku had mentioned being close since childhood. And since Junior high with that one girl. 

“Is it noisy at your place or something?” 

“No,” Tsukasa shakes his head, “it’s actually too quiet.”

Senku grins wide, “then if it’s too quiet you can always come here, I want to get every chance I can to study you Tsukasa.”

The fighter doesn’t take that at face value at all. Somehow he understood what Senku meant. Even if he wasn’t being as clear. Soulmates are an interesting thing. Even if Senku wants to research their hidden connection, he’s sure he was simply being friendly about it. He looks on the smaller teen with gentle eyes. He can see the way Senku falters at him.

“Alright then Senku, I’ll keep that in mind.”

• •

Dinner, or what you could call it, is actually quiet. Tsukasa finds then that Senku is a glutton. He eats with no time to waste. Sure he eats and chews thoroughly, makes sure he paces himself, but in the end he’s finished before Tsuaksa can blink. He’s polite then, not rushing the fighter as he eats. 

“I should probably get going, I don’t want to keep you up too late.”

“I’m the one who invited you.” 

He shrugs as he finishes his bowl. 

“Thank you for allowing me in your home Senku.”

Senku nods. “Yeah, after all these marks fade we should test it out on a new sensor.”

“Another?”

“Yes I’ll make some adjustments and see where we can go from there.”

Tsukasa nods. “Very well then Senku,” he stands, “just give me a heads up next time.”

“Yeah yeah, I promise.”

Tsukasa knew he would pull a last minute request again, and he can’t say he would be mad about it. 

• •

It’s been a a week or so since he went to Senku's to test out the sensor for the first time. Upon arriving for the second test, Tsukasa meets Taiju. He’s grinning and close to the opposite of Senku when it comes to demeanor. But he’s nice, and Tsukasa is immediately fond of his and Senku’s best friend dynamic. 

They were in the living room, it's just hit dusk and all of them had eaten Tsukasa's MMA fighter meal. Senku was laying on his side to set up a monitor to display on the TV so they would all be able to see it much more easily. Then he stopped talking. 

Tsukasa doesn't quiet notice at first, thinking they had all went into a nice silence. Then he has Taiju excitedly nudging him. The brunette looks over to him. 

" _Tsukasa_ " he whispers to him, " _He fell asleep._ " 

Tsukasa's eyes follow to the direction Taiju is pointing. Senku is still on his side, hardly squished between the TV stand and the wall. The black HDMI 1 pop up flashing in the corner. 

Slowly, the two of them peak over the head of the television. There are two wires in the scientists limp hands- one is plugged in but the other lays loose. His face is slack and he breaths in small, easy breaths. 

Tsukasa feels a blush creeping over his face. Senku was.. cute. Very cute in fact. There was no doubt that he was an attractive person- but to see him doing such a human thing like sleeping was something different. Tsukasa had already understood that they weren't going to play into the stereotype of young soulmates who pretend to fall hard for each other at their first meeting. Hell, he doesn't even know if Senku cared that they were supposed soulmates- it's all theory to him. 

"Should he be sleeping back there?"

"It's all good, he likes it that way." They both stand straight, "we should probably let him sleep- that pork stuff you made probably filled him up so much he couldn't resist sleep anymore."

Tsukasa takes off the new sensor helmet and removes the padding from his shoulders. He can't help but wonder how much sleep such an intelligent person could hold off on. Some of the smartest people on earth even refused themselves sleep- and knowing an up and coming renowned genius, Tsukasa can surely say it's because of the speed their brain runs. 

"How often does he just fall asleep like this?"

Taiju begins to quietly put their equipment away- like he had done this enough times to know how to clean up before putting Senku in a proper bed. 

"Not often anymore- ever since I got Byakuya to tell him to go to bed early or he'd worry." he folds a stand and laughs, "but ever since you two found each other, he hasn't even stopped to take a breath- it got him excited you know."

That's what he had said before, but Tsukasa couldn't help but wonder what that even meant. How could he, a single person who's connected to him by almost unknown means get excited enough to neglect his health for all of this?

"Should I stop enabling him this way?"

"No," Taiju quickly shakes his head, "don't stop!"

"Shhh" Tsukasa puts a finger to his lips and they hear the scientists breathing stir.

Taiju looks sheepish and lowers his voice while saying, "don't do that, he's having fun- well I can't tell you what to do but- but don't you want to see the outcome of the research too? I mean you don't say no to him so..." 

Tsukasa thinks on it a moment. Well, he hadn't said no as of yet because he was pretty interested. And his supposed soulmate was good company. Paired with Taiju, it makes him forget what lonely silence sounds like. Slowly he nods and Taiju smiles again. 

"Senku will figure out a sleep pattern like he always does."

The fighter isn't quite convinced on that, but he doesn't argue. Taiju had known Senku since they were children. 

After putting the equipment-- save for the monitor-- up, Tsukasa is the one to collect the sleeping scientist. He pulls the stand forward to get to him and chuckles at the red glare he receives. Senku doesn't like sudden wake up calls. 

He puts an arm under his knees and his back. Senku was as light as a couple of grapes. The scientist doesn't oppose to being picked up, but he does argue verbally. 

"We aren't finished."

"Another time Senku- you're clearly in need of some rest."

"Yeah man, getting us to come help you when you clearly aren't in the shape to be awake is bad for your health.”

"It's only six!" He looks up at Tsukasa and their eyes meet. It's as if he's just realized he's been picked up. His next words obviously catch in his throat. 

"Sounds like a good bedtime to me." Taiju laughs as he let's Tsukasa into the others room. It's as organized and put away and _nerdy_ as Tsukasa had imagined it. He only does a glance over it. Astronaut and rocket figures on his dressed. A Doraemon sticker stuck to the middle of his closet door. A periodic table pasted large on his wall. The body in his arms still unsure if it wants to flee or not. And as Tsukasa approaches his bed, Senku seems to have decided, tugging at one of his long strands of hair.

"Hey, you can put me down now!"

Senku yelps when Tsukasa dumps him onto the bed, the springs squeaking from his impact. Senku glares at him again, eyes squinted sharp at him for the drop.

"You said to put you down." Tsukasa smirks at him. Taiju is chuckling at the scene. It wasn't everyday you heard Senku sound that way either. 

"You’re really making me go to bed right now?"

"Afraid so."

Senku huffs and lays his chin atop one of his pillows. 

"Fine, but we have to finish- you have to make dinner again too."

"You can't just volunteer people to-"

"Sure, just get some sleep." Tsukasa cuts Taiju off and glances to him, "don't worry, I don't mind at all."

His concern vanishes in an instant into a big smile- happy about the news as well. 

They leave Senku laying in his bed, saying their own goodnights and promising to lock the door before leaving. 

Taiju doesn’t live far from Senku- at least Tsukasa has come to believe that about him. He walks along side him humming away some tune he’s never heard before. And before he can get out a word of goodbye as they get to the base of the stairs, Taiju asks. 

“Do you think Senku’s your soulmate?”

Tsukasa slowly blinks. Taiju is practically beaming at him. 

“I promised Senku not to make a big deal when meeting you but how can I not? Soulmates are so cool I’m so jealous of you two.” He grins. 

The question hadn’t really occurred to Tsukasa himself. Did he think Senku was his soulmate? He wasn’t very sure. He gets along with him. And his words plant a nice distraction from the endless quiet yet never ending noise within his own mind. 

“I don’t know,” The older teen puts a hand to his lip, the pads of his fingers pressing gently against his mouth, “I think he’s the first friend I’ve had in a long time.” 

Taiju practically squeals at his words. Tsukasa glances at him in worry. 

“I’m so happy for you two!”

“I wouldn’t get too excited though, after all it’s not like it means we’re fated lovers or anything- it’s simply-“

“Brain wave radio junk yeah I get it- Senku says that all the time!”

They’re walking now, but Tsukasa isn’t very sure where to. He’s headed to the train station and has no idea where Taiju lives. 

“Does Senku think we’re soulmates.” He had asked Senku before if he thinks they’re real- he’d given him an answer. Tsuaksa wonders if that really meant he thought they could be more than just.. Tsukasa shakes his head. He has other things to worry about. 

“Well, yeah- he has to, the proof is on your bodies isn’t it?” Taiju grins at him, “Senku might not think being soulmates means something amazing outside of science- but I’m certain he thinks it means _something_ \- why else would he have made that sensor?”

Taiju has a point. He’s a sentimental guy for sure. And his words are conveyed very fond when it comes to concerning Senku himself. Tsukasa smiles hopefully at the other. He isn’t really interested in all the lovey dovey mumbo jumbo like Taiju is, he doesn’t want to be, but he does believe it means something. And Senku is an interesting guy. 

If fate did make their paths cross. Then he would like to know why. After all, if such a thing exists he would say it has been quite unkind to him. To his sister too. 

“I’m interested to see the outcome of Senku’s research.” And he hopes whatever the outcome may be, he’s still able to be friends with him in the end.

**Notes for the Chapter:**

> Hmm I was thinking about changing the name of this fic. I feel like I should be answering the question. What is the meaning of destiny? I want to. But I’m unsure if I can do it in a satisfying way. Anyways, I hope you enjoyed this chapter!


	4. Knockout

**Summary for the Chapter:**

> Senku can make Tsukasa happy.

“Slow down!” Tsukasa slows his pace as he turns to look back at Senku who’s trying his best to catch up with him. 

Morning jogs were simply routine for Tsukasa. After that was to shower, have a coffee, and wait for school or whatever else awaited the day. And in all these years he hadn’t even thought of jogging these mornings with someone else. 

Senku had continued on testing things with him. But Tsukasa finally told him in return, he had to come jogging some mornings with him. It was no surprise how little stamina the scientist had. He practically looked one foot in the grave as he wobbled up to Tsukasa, grabbing his arm for support. 

“You can’t really expect me to keep up with you right?” Senku says in many breaths, sweat beading down his brow and dampening his hair. 

“Not particularly, but don’t you think it’s good for you to do this? Keep your body active as well as your mind?”

“Walking to school everyday is enough for me, thanks.” Senku wipes at his forehead with the sweatband he had attached to his wrist before leaving with Tsukasa that morning. “You do this all the time?”

“Every morning.” Tsukasa chuckles and passes the water bottle he keeps attached snug to his pants to the other. Senku takes it in kind, gulping down the water like it was his last breath. 

Senku lets off the bottle with a loud sigh of relief. He’s still panting but not as desperate as before. Tsukasa smiles as he takes the bottle back to drink from it. Senku had done good for, well, Senku. They were almost a mile in. Tsukasa typically does a five mile on Saturdays, but he wouldn’t tell Senku that. 

“We can stop today if you’d like,” he says, watching the others eyes light up, “I don’t want to push you too far.”

“I don’t want to wake up in a hospital bed either so I agree.” But they would have to walk back. It was easy for Tsukasa, but Senku’s legs are shaking and he moves them as if they are cramping. Tsukasa lowers himself and looks at Senku. 

“Cmon, I’ll take us back.”

“On your back like a child? I have legs.” Senku frowns. 

“Sure you do, but can you actually move?”

Senku nods and turns, starting to walk as if making a point. Tsukasa notes his shaky legs until his knees buckle on him and he’s plummeting to the ground. He’s thankful he was blessed with speed, catching the smaller before he meets the sidewalk. 

Senku looks up at him, frown only deeper. Tsukasa knew he didn’t like the idea of ridding piggy back. But no one but joggers were around this morning. Besides, they’re in their own world to care what they’re doing. 

“It’s faster if you don’t keep endangering yourself, take a rest while I get us back.”

His soulmate can only huff as he climbs upon his back. Legs lock around Tsukasa’s waist and the fighter can’t help but blush himself as he used his arms to hold Senku’s legs. It certainly wasn’t the first time he’d held him. The position reminds him of his little sister and the times before, when they had done sweet piggy back rides. 

Before they knew it, they were back at Senku’s apartment. 

“It’s Saturday, what are you in such a hurry to leave for?”

Senku is getting his sweaty shirt off and watching Tsukasa has he’s just excused himself from the home. 

Well, Tsukasa did have a match today. But it was much later in the evening. Senku knew that much. However, before matches he usually took a visit to his sister. That was something he had yet to mention to Senku. It wasn’t really anyone’s business but his own. Senku was his soulmate, and even though he’d been pondering what that even truly meant, right now it didn’t mean he could know his emotional vulnerabilities. He smiles at Senku, feeling almost bad for having excused himself so soon. 

“What? You gonna miss me?”

“You’re the one who wanted to go jogging with me, I just didn’t think you meant jog and leave.” Senku tried to feign a look that said he was uncaring of what choice Tsukasa made. But the fighter knew almost immediately by the way he glances to the side for a split second that he didn’t want him to leave just yet. 

He hums a moment. It was unfair of him, and in another perspective he knew it seemed like he was leaving because Senku couldn’t keep up with him. Tsukasa gives into that thought. He likes Senku, he’s one of the only people he could actually call a friend. 

“You’re right,” he rubs the back of his neck, “lets get breakfast together, my treat, but I’ll have to use your shower first.” Tsukasa wasn’t as sweaty as Senku, but he hated walking around in his sweat. 

His words seem to content Senku, who nods at him, not saying much else as he led him to the shower. It wasn’t big enough, well not really. Tsukasa has to dunk his head to get under the shower head at least. 

Senku cleans up after him. The silence in his home as he waits for him feels unavoidable. He almost hates it. 

Instead of occupying himself on his phone, Tsukasa doodles on his arm just to mess with the smaller. 

_171cm compared to 195cm, your shower is small._

He hears a chuckle come from inside the shower room and suddenly the silent evil in Tsukasa’s ears has vanished. 

•••

Tsukasa doesn’t usually have a good day before his matches. It’s usually quiet talk in a hospital room and then a meeting with his manager and the venue. Then a few work out rounds to get his body and mind prepared. Nothing too strenuous. 

Tonight he had only one match, the one that would determine if he was going on to the championships or not. It was a fight he’d been through before. And won. He doesn’t know at what point they had considered him _undefeated_ but the insinuation was nice. It certainly intimidated his competition. 

Senku had made most of his day rather relaxing. Just being a normal teenager was something he had forgotten how to do. But Senku had brought his inner immaturity right out of him. Even if Senku was an intelligent teenager, almost to the point Tsukasa wondered if he should even be in high school or not, he still has that childlike wonder in him. The one that talked to him about gaining materials in monster hunter and theorized star signs with him. 

And even at one point Tsukasa had embarrassingly admitted he still has a bra a fan threw at him. He’d been too in shock to put it down but no one told him what to do with it. He had wanted to return the frilly thing but somehow ended up taking it home with him. Senku called him a closet pervert for it. Which _no_ that wasn’t it at all! It was left in Tsukasa’s laundry room just hanging there. They were both sure that fan would probably be ecstatic to hear that, even though Tsukasa had hoped to return it someday. 

“Shishiou,” he looks up from the place on his skin he had written on early. Now he had washed the words away for his match, but he couldn’t help but smile to himself. “You get a girlfriend or something?”

Tsukasa looks at his manager like he hadn’t even noticed he’d been staring at his arm for the last five minutes. 

“No?”

“Well you look like you’ve been floating for the last ten minutes! Get your head in the game kid, you know this match is important.” Yeah, he’s on in less than an hour. His manager was right. Senku had put him in a good mood, so he’d have to do his best to win.

“Ah, right,” Tsukasa stands and stretches a moment, adjusting his shorts. “I’ll be right back, going to get some fresh air.” In all the fun he had that day he hadn’t gotten a chance to speak with his sister before his commute to the venue. Taking a moment outside wasn’t the same, but it’d give him the closure he needed before the match. 

Or, it would have. If he had made it that far. 

“Senku?”

“Tsukasa!” Taiju is right by the scientists side, holding quite literally all their snacks. Next to them was a girl, small and looking flustered. He hadn’t officially met her yet. She had been much to busy with her crafts club, creating things for Theatre club, to join them from what Taiju had said. But he had seen her around. 

“Hey! Didn’t expect to see you out here!” Taiju continues on. 

“Shhh Taiju he’s probably trying to be incognito.” The girl, Yuzuriha he thinks her name is, shushes him so he speaks lower. 

“Incognito? There’s no way a behemoth like you could do that.” Senku grins at him and Tsukasa feels a small embarrassment cross his cheeks. 

“Did you guys come to see my match?” He had never had anyone in his personal life go out of their way to do something like that. Not even his own parents. 

“Well...” Senku rubs the back of his neck. 

“Senku told us he won three tickets to the fight! Isn’t that amazing?” Taiju beams at the fighter who can’t help but gaze right on back to the smaller. 

“Ah, I see, I didn’t take you as the raffle type.” Tsukasa hadn’t heard of any giveaways for this particular match, but there was always private raffles with pre-bought tickets floating around. “I could have just given you tickets you know.” 

There’s no answer. “So who are you going up against?” Yuzuriha asks just before apologizing and introducing herself. “Sorry for not being able to formally introduce myself yet.” 

“That alright, if I win this match I’ll be going to the championships again, I’ve never faced this guy before so I’m told it will be interesting... something Ken?” He feels almost bad for not remembering his opponents name. 

“You’ll do great!” Taiju exclaims for him. 

“Yeah totally good luck!!!” Yuzuriha is beaming at him and he feels like these are the most sincere wishes he’s ever received. His eyes fix again on his soulmate. 

Their eyes meet and he’s really hoping for his praise. After their fun morning together, Tsukasa had almost forgotten about his work for once. 

“You’re opponent struggled to win his previous matches, plus his tactics are rather predictable so I have no doubts of you winning.”

“I didn’t know you were so into MMA Senku.” Yuzuriha says that, but she has a small smile on her face that totally says she’s teasing him. 

Tsukasa knew Senku didn’t have any interest at all in MMA already. But he knew his opponent. And he “won” tickets tonight. All total coincidences he’s _sure_. 

“Thanks, I’ll do my best.” With that they part. After all, he’d rather not his friends be harassed by any lurking press. Keeping conversation small was good enough to make it look like they’re just friends. 

•••

 _”Shishiooooooou Tsukaaasaaaa”_

Tsukasa always hates how the announcers drag out his name. He bites a bit on his mouth guard. He’s not one to show off. His large body does that for him. His opponent is about fifteen centimeters shorter than him. But he doesn’t look intimidated at all. His manager had given him the rundown of his opponents previous matches. Senku was right, he was predictable. 

The lights prevent him from finding the trio in the crowd, but he doesn’t mind. As the announcer is calling on his opponents name, Tsukasa feels a nice tingle flood his body. He glances down to his arm to watch the words _good luck_ appear on his arm. Senku hadn’t said it directly earlier. Tsukasa had understood what he’d meant, but it was a nice gesture to say it to him this way. Even if it was seconds before the match was starting. 

His match doesn’t feel long enough. As in, he feels like he’s in a spare with a weaker opponent. The guy tried to go for his jaw and then grab for his waist, but Tsukasa had dodged quickly and went in for a right hook. The guy had hit the rope edge of the rink. He tried to recover but Tsukasa must have struck him all too hard as he stumbled and was knocked flat out. He hadn’t went in for more strikes. It was clear from the others facial expression he was done in. It was disappointing. He wanted to give his friends a good show, but this was a straight knockout. The crowd is cheering and he watches as the other man comes back to life, stumbling with the help of the ref. But it’s clear Tsukasa has won. 

••

“Damn Shishiou who pissed you off?” One of the other fighters asks as he’s putting away his mouth guard. 

“No one actually,” he replies. 

“Keep throwing stunts like that and everyone is going to be scared to get in the rink with you.”

“Everyone should be,” he hears his managers drawl as he stands at the end of the lockers, “he’s wining the championship this year.”

“Don’t inflate his ego.”

Tsukasa chuckles to himself. No, he thinks he was the exact opposite of pissed off. He was calm. Empty stomached but not hungry. Happy, even. 

His phone vibrates the metal of his locker and he checks it. 

From: _Senku🚀🥬_

[ _That dude has a broken jaw for sure, I hope I never get on your bad side. This place is ten billion percent too loud for me so I’m going home and letting these two finish it off as a date._ ]

To: _Senku🚀🥬_

[ _I have to stay for the after party to meet with some sponsors. See you at school?_ ]

He hates how happy Senku’s reply [ _Of course._ ] makes him.

**Notes for the Chapter:**

> It’s been so long since this has updated oop. But I’ve had this chapter in mind for awhile. Tsukasa had finally found someone he can be himself around. Soulmate or not, he really is happy around Senku. 🥺
> 
> Btw I watched like a ton of MMA vids for this before finally deciding Tsukasa should just knock him out deadass XDD MMA fights are... kinda funny to watch?? Like it’s weird imagining Tsukasa in that situation even tho that’s what he DID. Mans undefeated XDD Anyways some matches were p interesting to watch so I recommend it.

**Author's Note:**

> Welcome welcome to the beginning of something I hope I’ll finish! XD I hope you enjoy!


End file.
